Strap clasp

ABSTRACT

A clasp with a locking flap (8) hingedly mounted between the arms (3a, 3b) of a yoke-shaped member (3) by means of a pin (9) extending through one portion (8a) of said flap (8). Said portion (8a) is shorter than the distance between the two arms (3a, 3b) so that the flap (8) is transversely translatable. The pin (9) has a straight portion (9c) partially inserted into a correspondingly shaped recess (13) in one arm (3b). The pin (9) is thus prevented from rotating about its own axis. The passage (14) in said portion (8a) of the flap which receives the pin (9) has an inlet (14a) shaped to fit said portion (9c) of the pin (9). A coil spring (15) on the pin (9) biases the flap (8) towards said portion (9c) of the pin (9). When the flap (8) is in the folded down or locking position, said portion (9c) of the pin (9) is inserted into the inlet (14a) of the passage (14), thereby locking the flap (8).

The present invention relates to a strap clasp provided with a locking device comprising a locking member articulated on the body of the clasp around a transversal axis, and which is able to occupy two positions, one, turned up, in which the clasp is unlocked, and the other one, turned down, in which the clasp is locked.

Clasps as hereabove mentioned are known per se. They are used for several applications, especially for the closing of straps for watches.

In these known clasps, the articulated locking member is, in most of the cases, constituted by a flap hold in its turned down position, of locking, by means of a protrusion which is resiliently deformable, of the flap and which is snapped to another element of the clasp. Such an arrangement does not exclude the risk of an undesired unlocking of the clasp.

The object of the present invention is to furnish means for maintaining the articulated locking member in a locking position which reduces the risks of an undesired unlocking.

This object is achieved by means as claimed in claim 1.

The drawing shows, by way of example, one embodiment of the object of the invention.

FIG. 1 is a perspective view of a clasp for watchstrap in its open position.

FIG. 2 is a sectional view of this clasp to an enlarged scale, passing through the articulation axis of the locking member, the latter being in its turned down position of locking.

FIG. 3 is a sectional view on the line III--III of FIG. 2.

FIG. 4 is a sectional view on the line IV--IV of FIG. 3.

FIG. 5 is a perspective view of a detail of this clasp, and

FIG. 6 is a sectional view similar to this of FIG. 2, the locking member of the clasp occupying its turned up position, of unlocking.

The clasp illustrated is generally designated by reference 1. It comprises two stirrup shaped members 2 and 3 between the arms 2a and 2b, respectively 3a and 3b of which are articulated the ends of the two parts 4 of a strap. The stirrup shaped member 3 carries, secured to its transversal portion, designated by 3c, by soldering for instance, a longitudinal small plate 5 the end of which is turned up at 5a in the shape of a gutter. This turned up portion 5a constitutes a hook intended to be hooked, when the clasp is closed, to a transversal small bar 6 disposed between the arms 2a and 2b of the stirrup shaped member 2.

The stirrup shaped member 3 carries, articulated thereon at 7 (FIG. 1), a hooking flap 8 intented to occupy a turned up position, represented in FIG. 1, in which the clasp is unlocked and a turned down position in which it closes the hook 5a, preventing the latter from releasing the transversal small bar 6.

The locking flap 8 is articulated between the arms 3a of the stirrup shaped member 3 by means of a shaft 9 represented in perspective in FIG. 5. This shaft is provided with a section 9a provided with a blind hole 10 in which engages the end of a screw 11 which is screwed in the arm 3a of the member 3. This screw 11 is itself locked by a screw 12 screwed in the arm 3a. The shaft 9 is prolongated by a section 9b of a smaller diameter, followed by a portion 9c, the shape of the cross-section of which is not circular (FIGS. 4 and 5), this portion 9c being itself followed by a terminal portion 9d engaging the second arm, 3b, of the member 3.

This second arm 3b is provided, on its inner face opposite the portion 9c of the shaft 9, witha milling 13 the width of which corresponds to this one of the portion 9c, in which is engaged the end of this portion 9c under the effect of the axial pushing exerted by the screw 11 on the shaft 9. It results from the engagement of the portion 9c of the shaft 9 with the milling 13 that the shaft 9 is prevented from rotating on itself.

The locking flap 8 is provided, along its rear edge, with a transversal portion 8a, which is thicker (FIG. 4), constituting a sleeve provided with a passage 14 traversed by the shaft 9. The length of this portion 8a is shorter than the distance separating the two arms 3a and 3b of the stirrup shaped member 3, so that the flap 8 can effect, besides its rotative locking movement around the shaft 9, a translation movement along this shaft. The end of the passage 14 situated opposite the arm 3b of the member 3 is provided, seen from the end, at 14a, with an opening portion the shape of which corresponds to the shape of the portion 9c of the shaft 9. At last, a coil spring 15, engaged on the end of the section 9a of the shaft 9, bears on the one hand on the arm 3a of the member 3 and on the other hand on the end of the sleeve 8a of the flap 8. This coil spring urges the flap 8 towards the right side of FIGS. 2, 3 and 6.

When the flap occupies his turned up position, in which it closes the hook 5a, the opening section 14a of the passage 14 is orientated, with respect to the shaft 9, in such a way that the portion 9c can engage the recess constituted by the opening 14a, that locks the flap 8 in its locking position, the shaft 9 being not able to rotate on itself.

When the user of the clasp acts on a pin 16 (FIG. 1) carried by the flap 8, for instance by means of one of his finger-nails, he can move the flap along the shaft 9, in the direction of the arrow 17 of FIG. 6, against the action of the return spring 15, thus bringing the portion 9c of the shaft 9 out from the recess 14a. The flap 8 can then be turned up and brought into the position represented in FIG. 1 in which the clasp is unlocked.

Owing to the arrangement as disclosed and represented, the flap 8 is perfectly locked in its turned down position, of locking, without risk of an undesired unlocking.

As a modification, the articulated locking member could present a shape different from a flap.

As a modification also, one could provide the case where the portion 8a of the flap would present a protrusion or a recess of a shape corresponding to a recess or to a protrusion of the inner face of the arm 3b of the stirrup shaped member 3.

It is to be noted that, in the example as disclosed and represented, the articulation shaft 9 of the flap 8 is held in position by a screw 11. One could however provide the case where this shaft could be held in position on the stirrup shaped member 3 by a device such as the one object of the Swiss Patent No 674.759 and of the corresponding European Patent No 0 373 184, both in the name of the same owners.

At last, the invention is not restricted to its application to watch clasps, as disclosed and represented, but could be applied to any strap, especially to belts, waistbands, and others. 

I claim:
 1. A strap clasp movable between an open and a closed position comprising, the clasp having a longitudinal axis, a locking member articulated around an articulation shaft which is positioned transverse to the longitudinal axis of the clasp, said locking member movable between a first turned up rest position and a second turned down working position, the locking member maintaining the clasp in its closed position when the locking member is in said working position, the locking member being operable to effect a translation movement parallel to said articulation shaft, a resilient return member associated with said locking member for said translation movement, said return member urging upon the locking member to maintain the locking member in said working position, said articulation shaft including a section of non-circular cross-sectional configuration, the locking member including a passageway for receiving said articulation shaft, said passageway having an ending portion of cross-sectional configuration which is substantially the same as the non-circular cross sectional configuration of the articulation shaft, whereby the ending portion of the passageway is engaged by the non-circular section of the articulation shaft when the locking member is in said working position.
 2. A clasp as claimed in claim 1 in which the shaft is prevented from rotating when the no-circular section of the shaft is engaged within the passageway.
 3. A clasp as claimed in claim 1 in which the clasp includes a body, said body having a generally stirrup shaped member with a pair of spaced apart arms, said locking member being articulated between said arms, the locking member having a portion which is engaged upon the articulation shaft, said last named portion having a length which is shorter than the distance separating said arms to permit the locking member to be moved in a movement of translation along said articulation shaft, said resilient member being a coil spring interposed between one of said arms and an end of said shaft which is spaced from the non-circular section thereof, said spring urging the non-circular section of the shaft into the ending portion of the passageway.
 4. A clasp as claimed in claim 1 in which the locking member includes a flap, said flap being engageable by a user to move the locking member from its working position against the action of said resilient return member to disengage the section of non-circular configuration of the articulation shaft from the passageway. 